The invention relates to cleaning cloths of the non-woven, woven or knitted types containing an adhesive and a tackifier which are effective to remove dust from a wide variety of surfaces. The cleaning cloths of this invention, for example, have been found to be highly effective in removing metallic particles produced by sanding automobile parts and body components in preparation for the painting of such parts and components.
Cleaning cloths of natural and synthetic fibers have been in use for many years. Without the addition of cleaning agents, their use is limited to simple cleaning tasks, often as an adjunct to the use of cleaning liquids and sprays in household use.
Non-woven cloths are particularly useful as cleaning cloths. In particular, non-woven cloths made by the hydro-entanglement process are highly effective for this use. The hydro-entanglement process is well-described in U.S. Pat. No. 3,537,945. Essentially, hydroentanglement process involves treating a web of fibers with jets cf high pressure water or other liquid which serves to "entangle" the fibers, i.e., to force the fibers from a position of alignment into one where the fibers individually are at various angles with respect to each other and become physically entangled to produce a hydroentangled fabric. The hydro-entangled fabric is exceptionally strong and soft, and it also contains voids which occur between the physical junctions of the fibers which are highly effective in assisting the pick-up and retention of dust and particles. Moreover, the hydro-entanglement process can be adjusted to produce a hydroentangled fabric which has visible apertures which also enhance dust and particle pick-up and retention.
The parent application Ser. No. 07/560,477, assigned to the assignee of the present application, discloses an invention which employs a hydroentangled fabric which is preferably (but not necessarily) of the aperture type, and which is preferably (but not necessarily) made of natural fibers, preferably from cellulosic fibers or other fibers. Further, the process of that invention involves impregnating the hydroentangled fibers with a pressure-sensitive adhesive and a tackifier while the hydroentangled fabric is still wet from the hydroentanglement process so that the pressure-sensitive adhesive and tackifier migrate completely throughout the hydroentangled fabric, as opposed to simply being applied on and remaining on the surface of the cloth.
U.S. Pat. No. 3,780,392 is directed to a dust cloth with a bioactive ingredient intended primarily for use in hospital and other places where bacteria, etc., are present and must be removed. In this patent, it is stated that the "tackifier is a pressure-sensitive adhesive"--which reflects the occasional confusion in the art between adhesives and tackifiers. More properly, adhesives, including pressure-sensitive adhesives, are one class of compounds and tackifiers are another class of compounds used to enhance the effectiveness of the adhesive. In the case of the invention of parent application Ser. No. 07/560,477, the tackifier increases the coefficient of friction and increases the ability of the pressure-sensitive adhesives to attract and retain dust and particles, especially metallic particles.
Thus, the '392 patent does not have a tackifier separate from a pressure-sensitive adhesive The "tackifier" [sic] disclosed is a "vinyl [sic] acetate copolymerized with a high molecular acrylic. A specific example of such a tackifier is 2-ethyl hexyl acrylate."
The '392 patent does not disclose the use of a wet cloth and thus requires surfactants and defoamers to wet the cloth which permits the cloth to take an even coating. The '392 patent also discloses the use of a lubricant for preventing the "tackifier" from adhering to a surface to which it is applied.
The concept of impregnating rags, as opposed to cloth, appears in U.S. Pat. No. 3,016,555, which discloses yet another chemical system involving a certain class of polyester resins dissolved in a plasticizer, the combination of which is referred to as a "tackifier". This patent does not disclose the use of both a pressure-sensitive adhesive and a tackifier.
Another reference involving impregnating cloths is U.S. Pat. No. 3,208,093, which discloses a tack cloth coated with synthetic resin conditioned with plasticizers and other modifiers so that the resin is not sticky to the touch and will not transfer to the surface being wiped. The "tackifier" ingredients are dispersible in an aqueous vehicle, e.g., an emulsion. The "tackifiers" disclosed include polyvinyl acetate, acrylic polymer, polystyrene and butadiene-styrene. The plasticizers are selected from phosphate and phthalate plasticizers.
Finally, U.S. Pat. No. 4,510,640 discloses a duster made of plastic film, one face being coated with a pressure-sensitive adhesive to afford a dust catching ability.
By contrast, the invention of parent application Ser. No. 07/560,477, as indicated, involves applying the pressure-sensitive adhesive and tackifier to the hydroentangled fabric while wet, so that the pressure-sensitive adhesive and tackifier can thoroughly impregnate the hydroentangled fabric. The result is a fabric which has a good hand, is soft and has excellent particle pick-up and does not leave chemical residue, nor does it stick to the surface to be cleaned. The invention of parent application Ser. No. 07/560,477 is very effective in picking up dust and metal particles and retaining them. This pick-up of dust and metal particles is achieved while the cloth is passed smoothly and quickly across a wide variety of surfaces, including metal surfaces. It was believed that the use of a tackifier greatly enhanced the particle pick-up capability of the pressure-sensitive adhesive and, further, that the thorough impregnation of the pressure-sensitive adhesive and the tackifier greatly enhanced particle retention. Probably, this occurs because the fibers in the hydroentangled fabric are coated with the pressure-sensitive adhesive/tackifier and thus are better able to cause the particles to remain in the voids by adhesive forces, as well as by being purely mechanically trapped.
The advantage of the invention of parent application Ser. No. 07/560,477 lies in the fact that the ability of the pressure-sensitive adhesive to pick up and retain dust and particles is enhanced by a tackifier. Furthermore, rather than being applied just to the surface of the cloth, the adhesive and tackifier are impregnated throughout the cloth.
In one particular application, namely, in the finishing of automotive parts, including body parts, the standard procedure is to sand the metal prior to painting. However, the sanding leaves a layer of metallic dust that must be completely removed before painting can begin. This is accomplished by the use of cleaning cloths and it is imperative that the cloths be inexpensive, be easily and smoothly slidable across the surface of the part, yet completely effective in picking up and retaining the metal particles.
The cloth of the invention of parent application Ser. No. 07/560,477 accomplished this important task effectively and economically with good cleaning performance, but did not solve the problems associated with drying out of the tackifier during storage. It was found that the shelf life of such tack cloth was curtailed due to drying out of the tack materials.